Here is my new design of a two stage amplifier with output mosfet run in class A. Output power is 4,8 W into 12 ohms for input of 2 V RMS. Máx Output power is 30 W into 8 ohms. Z input is 5k9 aprox.
In the attached file are the curves of total distortion vs. frecuency into 6, 8 and 12 ohms and for input of 0,001 V until 5 V RMS.
Sorry for my english!

Very nice circuit - your output stage is very close to something I am considering to use with tube driver, except I was not (until now) thinking of using the Aleph current source that you have employed. The Aleph is very well thought of, not surprised you find it sounds so good.

What is the purpose of the capacitor between emitters of the LTP input pair ?

__________________"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.

That capacitor connected across the emitters forms a low impedance at high frequency and raises the gain of the diff pair. This may get you Lowe distortion, but you will have then probably have to deal with reduced stability margins and possible TIM. I'd leave it out - its always better to trade a bit of distortion for stability in my view.